Transects provide information on the distribution of species in a given community. This is valuable when environmental factors change over the sample distance. Looking at the change in abiotic environmental factors with living organisms, transects are able to find correlations between plant and animal distribution and abiotic factors.
Also, transects provide information on community composition. Thus, transects do not only show the distribution of species over a given area, but the distribution of abiotic resources as well.